A Lighter Way to Control Light

Non-mechanical light scanner puts eyes where they are needed

0 Ratings

Imagine your team of Air Force Pararescuemen are organizing the rescue of a downed pilot in a war-torn village. The only maps of the village that exist are decades old and don't reflect changes to the terrain caused by months of shelling. No problem. Under cover of darkness, you pilot in a small drone equipped with a lightweight laser detection and ranging (ladar) system. A 3D image of the town begins to unfold before your eyes.

THE CHALLENGE

A sleek air-to-ground missile hurtles out of the clouds toward its target. A small, unmanned drone quietly looks around the corner of a building. A satellite silently circles Earth, mapping out the terrain behind enemy lines. Each of these tasks can save the lives of U.S. warfighters and each one requires a small, lightweight, low-power way of scanning light over large angles. With the development of novel non-mechanical beam steering technology, Boulder Nonlinear Systems (BNS) has decreased the scanner weight for these systems by ten times, and reduced the required power by a thousand.

WHY IT MATTERS

The Air Force relies on numerous airborne sensor systems to provide surveillance, guide munitions, and monitor the battlefield. These applications demand lightweight, low-power light steering. Ladar can provide new imaging capabilities to small, unmanned aircrafts and satellites while making smart munitions even smarter. Without a small, lightweight, and low-power means to steer light over large angles, however, these ideas are stuck on the ground. Current ladar systems require mechanical gimbals to scan a laser across a field of view (FOV) to generate the image and to aim the FOV. The gimbals add substantial weight, size, complexity and cost to these systems. By physically scanning massive optics, gimbals also require significant electrical power and their speeds are limited by inertia.

THE SOLUTION

Boulder Nonlinear Systems and North Carolina State University developed a novel electro-optic beam steering technology called the Liquid Crystal Polarization Grating (LCPG). LCPG can efficiently steer beams of light over large angles using simple, stationary, thin glass elements. By stacking these elements and combining BNS' optical phased array (OPA) fine-angle beam steering technology, BNS created a lightweight and low-power beam steerer that covers a wide FOV with high precision and no moving parts.

"This wide-angle non-mechanical light steering technology will allow incorporation of optical sensors on to smaller platforms while adding additional capabilities and reducing the maintenance overhead." — Steve Serati

HOW IT WORKS

How can you steer light with a thin piece of glass? The answer lies in liquid crystals. Liquid crystal polarization gratings are thin glass elements covered with a layer of liquid crystal. Liquid crystals possess a property called birefringence, through which different polarizations of light travel at different speeds through the crystal. By patterning the birefringence of the liquid crystal on the glass, a "polarization grating" can be formed in which light of a certain polarization gets steered into a particular angle. This steering is very efficient, with more than 99% of light going to the desired angle. By stacking these elements and using electrically controlled polarization switches in the stack, it is possible to steer light into discrete positions over wide angles without any moving parts. In this project, BNS combined this technology with a complimentary liquid crystal tool: optical phased arrays. Optical phased arrays are pixelated liquid crystal devices capable of steering light over small angles with analog control and very high precision. The resulting beam steering system can look anywhere in an 80° × 80° FOV with milliradian precision. Compared to a similar mechanical gimbal, this non-mechanical beam scanner reduces weight by an order of magnitude while reducing power consumption by over three orders of magnitude.

IMPACT FOR THE FUTURE

An optical scanner with such low size, weight, power, and cost requirements enables a host of new aerial technologies for the modern warfighter, including improved UAV- and satellite-based surveillance, better smart munition seeking, more robust munitions counter measures, and even high-energy laser strike applications.

Through this project, BNS brought their exclusive liquid crystal polarization grating technology to a new level by increasing the diameter and steering efficiency. Based on the results of this project, AFRL has funded development of a new production line for large aperture gratings at BNS with a projected cost savings of $99M over five years compared to existing mechanical scanners.

BNS holds exclusive rights to this beam steering technology, giving BNS a competitive edge in the marketplace and U.S. warfighters a competitive edge on the battlefield.

Liquid crystal polarization gratings drastically reduce the size, weight, and power requirements of optical scanners. A wide range of optical sensor packages will benefit from this technology. — Jay Stockley, Senior Scientist at Boulder Nonlinear Systems

Boulder Nonlinear Systems

www.bnonlinear.com

450 Courtney Way, Lafeyette, Colorado, 80026

Boulder Nonlinear Systems is a leader in the research and development of custom light control solutions, with more than 25 years of experience in delivering practical devices and systems to government, academic and commercial partners.

Steven Serati Steven Serati

Steven Serati

President and CTO

Jay Stockley Jay Stockley

Jay Stockley

Senior Scientist

Lance Hosting Lance Hosting

Lance Hosting

Senior Clean Room Technician

TOPIC TITLE:

Revolutionary Beam Steering Technology for Imaging Laser Radar

TOPIC NUMBER:

AF03-142

CONTRACT NUMBER:

FA8650-08-C-1312

For more exciting Air Force launch stories, visit launchstories.org

RATE THIS STORY

PREVIOUS

Faster, Better, Cheaper

NEXT

Finding the Right Stuff in Full Motion Video